1. Field of the Invention
The invention relates to a flexible conduit pipe for transporting fluids, which consists of two corrugated metallic tubes, an inner tube and an outer tube, which are arranged concentrically to one another and are separated from one another by an encircling annular space in which a spacing means is arranged (EP 0 952 382 B1).
2. Description of Related Art
Such conduit pipes are used for transporting a wide variety of fluids. These may normally be temperature-adjusted, heated or cooled liquids and gases. A special field of application is, for example, the transport of liquid gases, such as, for example, nitrogen and helium and also in particular methane. For this application, the conduit pipes must also have effective thermal insulation so that temperatures of less than −160° C., at which the gases are liquid, can be maintained. To this end, as little heat transfer as possible between outer tube and inner tube is also necessary, which also applies to the transport of heated fluids. The respective fluid enters the inner tube of such a conduit pipe as a rule at high speed, such that said inner tube—due to the corrugation—is “carried along” in the direction of flow of the fluid and is compressed at the end of the transmission section. The displacement of the inner tube in the outer tube caused by this leads to undesirable deformation of the conduit pipe overall.
In the flexible conduit pipe according to EP 0 952 382 B1 mentioned at the beginning, the spacing means consists of two strands of glass-fibre-reinforced plastic which are wound onto the inner pipe in opposite directions. In addition, nonwoven material is arranged as insulating material in the annular space, and a vacuum of between 10−1 mbar and 10−3 mbar prevails in the latter. This conduit pipe has proved successful in practice. Here, too, however, it is possible for the inner tube to be displaced in the outer tube despite the nonwoven material which virtually completely fills the annular space.